This invention is in the field of surgery, especially surgery to repair cartilage in joints such as knees, shoulders, or hips.
Background information on knee, hip, and shoulder joints, on cartilage tissue, and on “classical” techniques and devices that have been used for many years for surgical repair of damaged cartilage are discussed in numerous medical texts, such as Campbell's Operative Orthopedics, a five-volume treatise. Additional information is periodically issued by the American Academy of Orthopedic Surgeons in a series of books called “Orthopedic Knowledge Updates”; volume 6 in that series was issued in 1999.
As used herein, terms such as “surgery” and “surgical” include arthroscopic or other “minimally invasive” procedures which can be used to cut through tissue and insert a flexible membrane into a joint or other region of a limb or body.
The parent utility application cited above, Ser. No. 09/393,522, focuses mainly upon resorbable “scaffold” devices which can be used to help transplanted cells (mainly “chondrocyte” cells, which generate and secrete cartilage) generate new cartilage in a damaged joint such as a knee, hip, or shoulder. These improved scaffolds are inserted into a cartilage segment, such as on a femoral runner or tibial plateau inside a knee, in an area where a chunk of damaged cartilage has been removed. Briefly, the improved matrices use two different types of porous matrix materials. Both types of material are made of three-dimensional fibrous materials (such as collagen, the main type of fibrous protein which holds mammalian tissue together), but the two types of material have substantially different mechanical properties, mainly due to variations in fiber and crosslinking density, which can be manipulated and controlled during the manufacturing process. A relatively dense and stiff material, designed to withstand and resist a compressive load, is placed around the rim of the device and in internal “runners”. A softer and more open and porous matrix material, designed to promote maximally rapid generation of new cartilage, is nestled within the protected zones that are created by the denser load-resisting rim and runners.
That is just a brief overview; the contents of that application Ser. No. 09/393,522, are hereby incorporated by reference, as though fully set forth herein.
Application Ser. No. 09/393,522 also describes an advanced type of semi-permeable outer membrane that can be attached to the “articulating” outer surface of an implanted resorbable scaffold as described above. The scaffold will support the outer membrane with a degree of stiffness and resiliency that allows the membrane to mimic a healthy cartilage surface, which is also semi-permeable.
That type of semi-permeable membrane can be used independently of implantable resorbable scaffolds. For example, if properly implanted and secured, it can be used as a covering and protective layer for mildly damaged native cartilage which is suffering from certain types of abrasion and similar damage referred to by physicians as “chondromalacia”.
Accordingly, that type of surgically-implantable membrane is the subject of this current application, regardless of whether it is implanted along with and on top of a resorbable matrix, or attached as a protective surface layer to the top of mildly damaged cartilage.
One object of this invention is to disclose an improved semi-permeable membrane which can emulate and effectively replace the articulating surface of natural cartilage, for use in surgical repair of joints such as knees.
Another object of this invention is to disclose an improved type of semi-permeable membrane which can be used with any of a variety of resorbable matrix devices, including but not limited to the dual-material scaffolds described above, to increase the benefits offered by such devices for using transplanted cells to generate new cartilage inside a damaged joint.
Another object of this invention is to disclose an improved type of semi-permeable membrane which can be secured directly to an articulating cartilage surface that has been mildly damaged, such as by chondromalacia, to help protect and in some cases stimulate repair of such cartilage.
Another object of this invention is to disclose an improved type of semi-permeable membrane which can be used along with cell-growing scaffolds or other matrices that are being used to help replace or supplement tissue in an internal organ, such as a liver, spleen, pancreas, and possibly a heart.
These and other objects of the invention will become more apparent through the following summary, drawings, and description of the preferred embodiments.